GUS-W-9987248.

Release announcement:
https://www.python.org/downloads/release/python-3100/
https://blog.python.org/2021/10/python-3100-is-available.html

More detailsed "What's new":
https://docs.python.org/3.10/whatsnew/3.10.html

For this release, a new version of the buildpack's Python build script has been
added, which includes some long-overdue improvements:
- enables PGO (`--enable-optimizations`)
- enables loadable SQLite extensions (`--enable-loadable-sqlite-extensions`)
- enables strict configure option checking (`--enable-option-checking=fatal`)
- the make invocation now uses concurrency (!!)
- the test module cleanup step now also removes the `idle_test` directory

These bring our Python builds closer in-line with those used elsewhere, for example:
https://github.com/docker-library/python/blob/d65295b73bc2c711de96caeba17501d1a81b6a5c/3.9/buster/Dockerfile#L43-L45

For docs on the configure options, see:
https://docs.python.org/3.10/using/configure.html

Fixes #488.
GUS-W-8060029.
GUS-W-9093281.

Bumps [rubocop](https://github.com/rubocop/rubocop) from 1.22.0 to 1.22.1.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop/compare/v1.22.0...v1.22.1

)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [rubocop](https://github.com/rubocop/rubocop) from 1.21.0 to 1.22.0.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop/compare/v1.21.0...v1.22.0

)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [rubocop-rspec](https://github.com/rubocop/rubocop-rspec) from 2.4.0 to 2.5.0.
- [Release notes](https://github.com/rubocop/rubocop-rspec/releases)
- [Changelog](https://github.com/rubocop/rubocop-rspec/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop-rspec/compare/v2.4.0...v2.5.0

)

---
updated-dependencies:
- dependency-name: rubocop-rspec
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [rubocop](https://github.com/rubocop/rubocop) from 1.20.0 to 1.21.0.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop/compare/v1.20.0...v1.21.0

)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

GUS-W-9858039.

https://www.python.org/downloads/release/python-3615/
https://www.python.org/downloads/release/python-3712/
https://blog.python.org/2021/09/python-3712-and-3615-security-updates.html

GUS-W-9858035.
GUS-W-9858038.

GUS-W-9833138.

https://www.python.org/downloads/release/python-3812/
https://www.python.org/downloads/release/python-397/

GUS-W-9093278.
GUS-W-9832570.

Bumps [parallel_split_test](https://github.com/grosser/parallel_split_test) from 0.9.1 to 0.10.0.
- [Release notes](https://github.com/grosser/parallel_split_test/releases)
- [Commits](https://github.com/grosser/parallel_split_test/compare/v0.9.1...v0.10.0

)

---
updated-dependencies:
- dependency-name: parallel_split_test
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [rubocop](https://github.com/rubocop/rubocop) from 1.19.1 to 1.20.0.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop/compare/v1.19.1...v1.20.0

)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [rubocop](https://github.com/rubocop/rubocop) from 1.19.0 to 1.19.1.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop/compare/v1.19.0...v1.19.1

)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [rubocop](https://github.com/rubocop/rubocop) from 1.18.4 to 1.19.0.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop/compare/v1.18.4...v1.19.0

)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

The GitHub action `actions/checkout` now only shallow clones the Git
repo as of v2+, meaning the Check Changelog action fails with:
`fatal: ambiguous argument 'remotes/origin/main': unknown revision or path not in the working tree.`

To fix, an explicit `git fetch` has been added of the HEAD of the default branch.

In addition, the event types on which the check is run has been updated
to include missing event types:
https://docs.github.com/en/actions/reference/events-that-trigger-workflows#pull_request

Refs GUS-W-9728468.

Bumps [actions/checkout](https://github.com/actions/checkout) from 1 to 2.3.4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v1...v2.3.4

)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

See:
https://docs.github.com/en/code-security/supply-chain-security/keeping-your-dependencies-updated-automatically/about-dependabot-version-updates#supported-repositories-and-ecosystems

I've also changed the frequency to daily (so we don't have to wait as long),
and removed the custom label, so we get the automatic per lang labels.

Refs GUS-W-9678950.

Bumps [rubocop](https://github.com/rubocop/rubocop) from 1.18.3 to 1.18.4.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop/compare/v1.18.3...v1.18.4

)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [rubocop](https://github.com/rubocop/rubocop) from 1.18.2 to 1.18.3.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop/compare/v1.18.2...v1.18.3

)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [rubocop](https://github.com/rubocop/rubocop) from 1.17.0 to 1.18.2.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop/compare/v1.17.0...v1.18.2

)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Closes GUS-W-9531702.

https://blog.python.org/2021/06/python-396-3811-3711-and-3614-are-now.html
https://www.python.org/downloads/release/python-3614/
https://www.python.org/downloads/release/python-3711/
https://www.python.org/downloads/release/python-3811/
https://www.python.org/downloads/release/python-396/

Closes GUS-W-9093277.
Closes GUS-W-9528811.
Closes GUS-W-9531329.
Closes GUS-W-9531340.

Bumps [rubocop](https://github.com/rubocop/rubocop) from 1.16.1 to 1.17.0.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop/compare/v1.16.1...v1.17.0

)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [rubocop-rspec](https://github.com/rubocop/rubocop-rspec) from 2.3.0 to 2.4.0.
- [Release notes](https://github.com/rubocop/rubocop-rspec/releases)
- [Changelog](https://github.com/rubocop/rubocop-rspec/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop-rspec/compare/v2.3.0...v2.4.0

)

---
updated-dependencies:
- dependency-name: rubocop-rspec
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [rubocop](https://github.com/rubocop/rubocop) from 1.16.0 to 1.16.1.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop/compare/v1.16.0...v1.16.1

)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Bumps [rubocop](https://github.com/rubocop/rubocop) from 1.15.0 to 1.16.0.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop/compare/v1.15.0...v1.16.0

)

---
updated-dependencies:
- dependency-name: rubocop
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

The Heroku-16 stack reached end-of-life on May 1st, 2021, and from
June 1st, 2021, builds will be disabled.

This removes support for testing against Heroku-16 in CI, and also
for building new Python binaries for the stack.

This change is non-breaking as it only affects development (hence why
it's landing a few days early), however a changelog entry has been added
regardless, for improved visibility into the support status of the stack.

Closes GUS-W-9329579.

Closes GUS-W-9318135.

Since the Cedar-14 stack build system no longer exists, so this code
will never be run.

Closes GUS-W-9310936.

By default if Django is installed and a `manage.py` file found, the
buildpack will run Django's `collectstatic` command at the end of the
build.

This step can be skipped by setting `DISABLE_COLLECTSTATIC=1`:
https://devcenter.heroku.com/articles/django-assets#disabling-collectstatic

However previously, if `DISABLE_COLLECTSTATIC` was instead set to `0` or
the empty string (such as when toggling it on and off during debugging),
then collectstatic would still be skipped.

This behaviour was made more confusing due to there being no build output
that explained why collectstatic was being skipped.

Now:
* Using values of `0` or the empty string are treated the same as if
  `DISABLE_COLLECTSTATIC` was not set at all (all other values are
  unaffected).
* If `collectstatic` is skipped (either due to that env var, the legacy
  skip file, or because a `manage.py` file is not found), then the build
  output now contains the reason why.
* A deprecation warning is output when collectstatic is skipped via the
  legacy `.heroku/collectstatic_disabled` file method.

I've also added some more tests around collectstatic, since there was
only one before, and refactored the collectstatic step script to use
early returns for improved readability.

See:
https://heroku.support/950668
https://heroku.support/986549

Closes GUS-W-8813947.

Bumps [rubocop](https://github.com/rubocop/rubocop) from 1.14.0 to 1.15.0.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop/compare/v1.14.0...v1.15.0

)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Since otherwise format-on-save will remove the focus annotations
(that make rspec run just the specified test) whilst developing locally.

The rule is still enabled, so will prevent accidentally committing the
annotations (which would disable part of the test suite in CI).

Closes GUS-W-9303487.

[skip changelog]

* The release script now runs `git fetch` prior to determining which
  commit to tag, preventing tagging a stale ref.
* `buildpacks:versions` is now run after publishing, to save having
  to do so manually each time to print the release time/status.
* The unused `{previous,latest}-version` tag feature has been removed.
* The script can now be run via `make publish` for consistency
  with other buildpack workflows.
* Miscellaneous output formatting/bash best practices fixes.

Closes GUS-W-8813922.

Bumps [rubocop](https://github.com/rubocop/rubocop) from 1.13.0 to 1.14.0.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop/compare/v1.13.0...v1.14.0

)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Closes GUS-W-9219065.

https://www.python.org/downloads/release/python-3810/
https://www.python.org/downloads/release/python-395/

Closes GUS-W-9093272.
Closes GUS-W-9093274.

Bumps [rubocop-rspec](https://github.com/rubocop/rubocop-rspec) from 2.2.0 to 2.3.0.
- [Release notes](https://github.com/rubocop/rubocop-rspec/releases)
- [Changelog](https://github.com/rubocop/rubocop-rspec/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop-rspec/compare/v2.2.0...v2.3.0

)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Closes GUS-W-9183201.